MXPA99009621A - Preparation of copper-indium-gallium-diselenide precursor films by electrodeposition for fabricating high efficiency solar cells - Google Patents

Abstract

A photovoltaic cell (10) exhibiting an overall conversion efficiency of 13.6%is prepared from a copper-indium-gallium-diselenide precursor film (18). The film (18) is fabricated by first simultaneously electrodepositing copper, indium, gallium and selenium onto a glass/molybdenum substrate (12/14). The electrodeposition voltage is a high frequency AC voltage superimposed upon a DC voltage to improve the morphology and growth rate of the film (18). The electrodeposition is followed by physical vapor deposition to adjust the final stoichiometry of the thin film (18) to approximately Cu(In1-x,Gax)Se2, with the ratio of Ga/(In+Ga) being approximately 0.39.

Description

PREPARATION OF DISELENURE PRECURSOR FILMS OF COPPER, INDIO AND GALIO BY ELECTRODEPÓSITO FOR THE MANUFACTURE OF SOLAR CELLS OF HIGH EFFICIENCY BACKGROUND OF THE INVENTION 1. Field of the Invention The field of the present invention relates to the preparation of thin film semiconductor devices. More particularly, the present invention relates to electrodeposition of copper, indium and gallium diselenide films for solar cells. 2. Description of the Related Art The thin films of copper-indium-diselenide ternary chalcopyrite (CulnSe2) and copper, indium and gallium diselenide (Culn-i.xGaxSe2), which generically refer to Cu (ln, Ga) Se2, CIGS or simply CIS, have become the target of considerable interest and study for semiconductor devices in recent years. Sulfur can also be, and sometimes is replaced by selenium, as the compound sometimes also refers more generically as Cu (ln, Ga) (Se, S) 2 so that it covers all possible combinations. These devices also refer to the l-III-VI2 devices according to their constituent elementary group. These devices are of particular interest for absorber applications of photovoltaic device or solar cells. For photovoltaic applications, the p-type CIGS layer is combined with a n-type CdS layer to form a p-n heterounited CdS / CIGS device. The direct energy space of CIGS results in a large optical absorption coefficient, which rotates to allow the use of thin layers on the order of 1 - 2 μm. An additional ntage of CIGS devices is their long-term stability. Several methods have been reported for the manufacture of thin films of CIGS. Some of the first techniques involve heating copper and indium on a substrate in the presence of a gas containing selenium, including H2Se. Heating the copper and indium films in the presence of a gas containing selenium is known as selenization. One disntage of selenization with H2Se is that the H2Se gas is highly toxic, which is why there are serious risks for humans in large-scale production environments. In the patent of E.U.A. No. 5,045,409, Eberspacher et al., Describe depositing copper and Indian films by projection of magnetron sparks and the deposit of a film.

Selenium by thermal evaporation, followed by heating in the presence of several gases. Other methods for the production of CIS films include Bean Epitaxy Molecular, electrodeposit either by single or multiple steps and the vapor deposit of a single crystal and polycrystalline films.

Although steam deposition techniques have been used to give solar cells with high efficiencies such as seventeen percent (17%), vapor deposition is expensive. Consequently, solar cells made by vapor deposition have generally been limited to devices for laboratory experimentation and are not suitable for large-scale production. On the other hand, thin film solar cells made by electroplating techniques are generally much less expensive. However, solar cells produced by electrodeposite generally suffer from low efficiencies. For example, in Solar Cells with Improved Efficiency Based on Electrodeposited Copper Indium Diselenide Thin Films, NCED MATERIALS, Vol. 6. No. 5 (1994), Guillemoles and others, report solar cells prepared by electrodeposition with efficiencies in the order of 5.6% . SUMMARY OF THE INVENTION Accordingly, it is a general object of this invention to provide an improved process for the manufacture of high quality thin film Cu (ln, Ga) Se2 solar cells. It is also an object of this invention to provide low cost and high quality thin film solar cells that have high conversion efficiencies. It is a further object of this invention to provide a process for producing thin films of Cu-ln, Cu-Se, Cu-ln-Se and Cu-ln-Ga-Se that have applications in solar and non-solar cells.

It is still a further object of this invention to provide a process for electrodeposition of a thin film solar cell precursor containing gallium. To achieve the foregoing and other objects and advantages in accordance with the purpose of the present invention, as it is modalized and broadly described herein, the process of this invention includes the electrodeposition of a CuxlnyGazSen layer (x = 0-2, and = 0-2, z = 0-2, n = 0-3), preferably using direct current in combination with high frequency alternating current. Electrodeposition baths containing copper 0.1-0.2 molar units (M), 0.05-0.15 M indium units obtained from indium chloride, 0.05-0.15 M gallium units obtained from gallium chloride, ions of seletal from 0.01-0.03 M and at least 0.3 M lithium chloride was found to produce simultaneous co-electrodepositing of copper, indium, selenium and appreciable amounts of gallium with a good morphology, when an electrodeposition potential is applied which has a high frequency alternating current superimposed on a DC current. After the simultaneous co-electrodeposition, the additional material was deposited vapor to adjust the final composition of the very closed deposited film for Cu (ln1-xGa) Se- < stoichiometric This unique two-step film deposition process allows precursor metal films to be deposited by economical electro deposit and then adjusted using the more expensive but more accurate technique for physical vapor deposition to bring the final film to scale stoichiometric desired The solar cells are then completed as for example by chemical bath deposit (DBQ) of CdS followed by ZnO sparks, and the addition of two-layer metal contacts as well as optional anti-reflective coating. A solar cell made in accordance with the process described in the present achieves a device conversion efficiency of 13.6%. This represents a significant improvement over the 9.4% of the conversion efficiency device described in the patent application of E.U.A. Series Number 08 / 571,150, now the Patent of E.U.A. No. [to be assigned], of which this request is a continuation in part. The present invention also includes electrodeposition solutions and process parameters whereby gallium can be co-electrodeposited in appreciable amounts together with copper, indium and selenium, while still obtaining a densely packed morphologically uniform film to be processed in a photovoltaic cell. This co-electrodeposition of gallium also increases the amount of stoichiometric adjustment that should be made by the last step of PVD. The additional objects, advantages and novel aspects of the present invention will be set forth in part in the description of the following, and in part will be apparent to those skilled in the art upon review of the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a cross-sectional view of a CIGS photovoltaic device prepared in accordance with the present invention. FIGURE 2 is a cross-sectional view of the conductive zinc oxide layer 28 shown in FIGURE 1. FIGURE 3 is an electron scanning electron microscope photograph of the electrodeposited precursor film of Example 1 herein invention. FIGURE 4 is a graph of the Auger electron spectroscopy analysis for the cell of Example 1. FIGURE 5 is a graph of the Auger electron spectroscopy analysis for the cell of Example 2. FIGURE 6 is a graph of the Auger electron spectroscopy analysis for the cell of Example 3. FIGURE 7 is the X-ray analysis that results in the electrodeposited film and the finished films of Examples 1-3. FIGURE 8 is a graph of efficiency of relative quantum versus wavelength for the cells of Examples 1-3. FIGURE 9 is a graph showing the Current versus Voltage characteristics of the cells of Examples 1-3. DETAILED DESCRIPTION OF THE PREFERRED MODALITIES The present invention includes an essentially two-step process for the fabrication of high quality low-cost thin film CIGS semiconductor devices., which exhibits photovoltaic characteristics and especially adapts to solar cell applications. In the first step, a precursor film of CuxlnyGazSen (x = 0-2, y = 0-2, z = 0-2, n = 0-3) is electroplated onto a substrate such as a glass coating with molybdenum. This first step can include a single process and electrodeposition bath for counter current of electrodeposition gallium with other elements, as well as a single use of an alternating current together with a direct current. The second step is a physical vapor deposition of copper, indium, gallium and / or selenium. In this second step, the composition of the overall film is completely controlled so that the resulting thin film is very close to Cu (ln1-xGax) Se2 stoichiometric. These steps can be carried out on substrates having long surface areas. Consequently, the processes of the present invention allow the long area, high efficiency solar cells to be produced economically. Referring now to FIGURE 1, the CdS / CIGS photovoltaic device 10 includes a substrate 12 which may be, for example, soda-limestone silica glass or amorphous glass 7059. The substrate 12 also includes a contact layer 14 reinforcing molybdenum, approximately 1-2 μm thick. Molybdenum can be deposited using the DC sparks projection of a cylindrical rotation magnetron target (OMRC). To improve the adhesion between the Mo 14 layer and the precursor film can be deposited, an additional adhesion layer 16 of copper can also be deposited by electrodeposition. After the Mo 14 layer and the optional copper adhesion layer 16 have been deposited, the substrate could be degreased as, for example, with propanol and dried in flowing nitrogen gas. A metal precursor film 18 is then deposited by electrodeposition. The precursor film contains one or more of the copper, indium, gallium and selenium elements. The electrodeposition is generally a less expensive method of depositing these metals than the vapor deposit. However, it is not possible to control the metal relationships deposited during electrodeposition precisely as desired. As a result, the main CIS layers deposited entirely by electrodeposition will produce low conversion efficiencies. In the present invention, the electrodeposition step is integrated with the vapor deposition step in the following manner. This allows the precursor metal to be deposited in bulk using an economical electrodeposition step followed by a vapor deposition step to complete the control of the final metal ratios. This results in economical production and even high efficiencies of the resulting cell. The metal precursor film composition 18 is generally denoted as CuxlnyGazSen (x = 0-2, y = 0-2, z = 0-2, n = 0-3). The metal precursor film 18 could be deposited at approximately 1-3 μm in thickness, with the thickness being controlled by coulombometric measurements.

It has been found that electrodeposing the films using an AC voltage in addition to a DC voltage produces improved results. An AC voltage improves the morphology of the film. It is also thought that the AC voltage improves the nucleation (growth) of the thin film allowing the additional nucleation centers to be created. For a fully aqueous platinum solution, the applicable DC voltage varies from about 1-5 VDC, with a preferred voltage of about 3 VDC. Improved results can be obtained by overlaying an AC voltage of 0.2-5.0 VAC at 1-100 KHz, with preferred values of approximately 3.5 VAC at 10-30 KHz. The plant solution is adjusted to give a pH of about 1.0 to 4.0 and more preferably about 1.4 to 2.4. the avocado solution could preferably be about 10 ° C to 80 ° C and more preferably about 24 ° C. Adding a supporting electrolyte for the silver bath can further increase the conductivity of the silver solution, allowing a further increase in the electrodeposition regime. It has been found that salts such as NaCl, LiCl, or Na 2 SO, may be suitable support electrolytes for use with certain embodiments of the present invention. In completely aqueous solutions, the electrolysis of molecules that start to occur to an undesirable degree at voltage levels that are too high. The resulting O2"and OH" ions combined with the deposited metal ions or metals deposited to form oxides of undesirable metals and hydroxides on the precursor film 18. To overcome this disadvantage, the water in the plating solution can be either partially or completely replaced by one or more inorganic solvents such as dimethyl sulfoxide (DMSO). Increasing the organic solvent content of the electrodeposition solution allows for the cathodic potential that can be increased without unacceptably increasing the metal oxide and the hydroxide formation regimes. The increased cathode potential increases the deposition rate of the precursor films. An additional advantage is that increasing the cathodic potential increases the gallium deposition regime in relation to deposition regimes of other deposited metals. Therefore, using a solution containing one or more organic solvents allows the cathodic potential to be selected from a wide variety such as achieved or more desired stoichiometry of the precursor film as it was deposited 18. When an organic solvent is used, the The preferred cathodic potential is approximately 3-10 VDC and 0.2-5.0 VAC at approximately 1-100 KHz. The value of approximately 5 VDC and 0.45 VAC at approximately 18.1 KHz was found to give good results. As the number of elements that can be electrodeposited simultaneously increases, the difficulties increase. Obtaining the simultaneous electrodeposition of four elements in pre-defined relationships with good morphology, for example, can be an extremely difficult task. Parameters that can be adjusted simultaneously include but are not limited to: total solution molarity, relative molarities of constituents, from which compounds the desired constituent elements, pH, temperature, voltage, waveform characteristics and electrolytic fluid can be obtained. Due to the simplified complexities in the simultaneous co-electrodeposit, it is thought that gallium had never been co-electrodeposited successfully together with copper, indium and selenium to produce a photovoltaic device. The present invention includes solutions and process parameters by which gallium can be co-electrodeposited in appreciable amounts together with three other constituent elements of CIGS. If desired, a second electroplating solution can be employed to adjust the stoichiometry of the electrodeposited film before the vapor deposition phase. For example, a first electrodeposition step can produce a CIGS precursor film with less gallium than optimally desired. Although the gallium content may be increased during the vapor deposition phase, it may be less costly to deposit a certain amount of gallium using a second electrodeposition solution to form a thick stoichiometric fit prior to the procedure for fine stoichiometric adjustment to the vapor deposition step. Another potential motivation for using a second electrodeposition solution achieves a gradient composition in the deposited film, as suggested by the U.S. Patent. No. 4,335,266 presented to Michelsen et al., Which is incorporated herein by reference for its composition teachings-thin CIGS films added for the solar cell and other applications. Still another route to achieve the gradient composition during the electrodeposition is by varying the process parameters such as cathodic potential, ionic concentrations, pH or temperature, as the electrodeposition proceeds. Several examples of electrodeposited precursor films manufactured in accordance with the present invention are given. These examples include Cu-ln-Ga-Se, In-Se, Cu-Se, and Cu-ln-Se, precursor films. The solution for the co-deposition of the four elements includes the elements of each element of copper, indium, gallium and selenium. Metal ions can be supplied in the form of dissolved metal salts. For precursor films that do not contain gallium, gallium could be added to raise the energy space. In the following discussion and claims, the electrodeposition potential is expressed in terms of a voltage without specifying a positive or negative voltage. It should be understood that the working electrode or substrate on which the thin film is deposited can be connected as the electrodeposition cathode, with the counter electrode being connected as the anode. Consequently, the electrodeposition voltages described herein, should be understood as negative voltages. According to this agreement, where the electrodeposition voltages are expressed as, eg, "at least 1.0 volts", this indicates that an electrodeposition voltage that is less than negative as -1.0 volts with respect to the opposite electrode which will be applied to the substrate. Treating the electrodeposition voltages as unassigned voltages should be understood as merely an easy way of reference to the absolute potential difference between the electrodes. After the precursor film 18 has been electroplated it must be cleaned. A suitable method is to rinse the precursor film 18 with deionized water and dry it in nitrogen gas flow. After the precursor film 18 has been cleaned, an additional layer of copper, indium, gallium and / or selenium is deposited by physical vapor deposition to adjust the final film composition at ratios of approximately Cu = 1-1.2: (IN, Ga) = 1-1.2: Se = 2-2.5 and more preferably approximately 1: 1: 2. By controlling the In / Ga ratio the energy space between the CdS and the CIGS layers can be adjusted to the optimum or near optimal value. An energy space of approximately 1.45 eV is considered optimal for the conversion of terrestrial solar energy, and is achieved by an In / Ga ratio of approximately 3: 1. For cells prepared according to the method described herein, an atomic ratio of Ga / (ln + Ga) of 0.34-0.50 is preferred, with a ratio of 0.39 producing the efficiency increase observed. The temperature of the substrate (precursor film) could be 300 ° C to 600 ° C during PVD, and preferably about 550 ° C.

After PVD, the films can be annealed. Annealing improves the homogeneity and quality of the films. A high quality CIGS film is one that does not exhibit an excessive amount of copper nodules, voids or unoccupied spaces in the film, which could completely reduce conversion efficiencies. It was found that annealing the films from 250 ° C to 500 ° C in a vacuum, followed by slow cooling at a rate of about 3 ° C / min. to avoid thermal shock, it gives good results. Because selenium has a higher vapor pressure than copper, indium or gallium, selenium can escape from the film during the high-temperature steps of vapor deposition and annealing. To compensate, the atmosphere during these steps may contain a moderate overpressure of selenium. In this preferred embodiment, the film is selenized at a rate of 5-100 A / s during the temperature reduction of PVD at the annealing temperature.

Once the CIGS layers 18 and 20 were collectively deposited and annealed, a n-type semiconductor thin layer 22 comprising cadmium sulfide was then deposited. The CdS layer 22 is preferably deposited by the chemical bath tank (DBQ) to a thickness of approximately 200-1000 A. The DBQ bath can be prepared from 0.08 gm of CdS0, 2.5 gm of thiourea and 27.5 gm of NH OH dissolved in 200 ml of water. The deposition temperature could be about 40-80 ° C. A layer 28 of broad conductive intermediate band n-type semiconductor materials is then deposited. In the preferred embodiment, the layer 28 comprises two layers of zinc oxide 24 and 26 shown in FIGURE 2. The first layer of zinc oxide 24 is deposited with RF bombardment at approximately 0.62 watts / cm 2 in an argon plasma. a pressure of 10 millitor. The second layer of zinc oxide 26, comprising about 1-5% zinc oxide contaminated with Al203, is also prepared using RF bombardment at approximately 1.45 watts / cm2 in an argon plasma at a pressure of 10 millitorr. In an illustrative embodiment, the resistivity of the first layer was 50-200 ohm / cm2 and the resistivity of the second layer was 15-20 ohm / cm2. The transmission capacity of the global ZnO layer was 80-85%. The two-layer metal contacts 30 could then be prepared with an e-beam system or other techniques. In an illustrative embodiment, a first metal contact layer had a thickness of 500-1000 A of Ni and the second metal contact layer had a thickness of 1-3 μm A1. The metal contacts 30 will generally extend in fine grid lines through the collector surface of the device and connected to a suitable current collector electrode (not shown). The efficiency of the resulting device was further increased by adding an anti-reflection coating 32, such as a 600-1000 A layer of MgF2 by the electron beam. A device prepared according to Example 3 below exhibited a conversion efficiency of 13.6%.

Example 1 A thin film containing copper, indium, gallium and selenium was deposited on a glass substrate coating with approximately 500 A of Mo, and processed in a photovoltaic cell. The thin film was obtained by preparing a solution containing copper, indium and selenium ions and also includes gallium ions in concentrations of at least 0.05 molar and at least 0.3 molar LiCl. More particularly, the electrodeposition bath comprised 2.1286 gm of Cu (NO3) 2-H20, 7.9625 gm of lnCl3, 1.3929 gm of H2Se03 and 9.2063 gm of Ga (No3) 3 and 14.08 gm of LiCl dissolved in 450 ml of water. The resulting bath comprises approximately 0.014 M copper, 0.08 M indium, 0.08 M gallium and 0.023 M selenium ions. The pH was adjusted to 1-2. The deposit proceeded at 24 ° C. The substrate was used in the working electrode and a platinum gauze was used as the opposite electrode in a two-electrode system. The electrodeposition voltage comprised a CD component of at least 0.5 volts. More particularly, the electrodeposition voltage comprises a DC voltage of at least 1.0 volts and an AC voltage of at least 0.5 V at a frequency of at least 1.0 KHz superimposed on it. Even more particularly, the electrodeposition voltage comprised a DC component of 3.0 volts and an AC component of 3.5 volts with pulses at 20 KHz superimposed thereon. The voltage was supplied by an energy source obtained from Team Specialty Products Corporation of Albuquerque, New Mexico. The AC component is nominally a square wave. However, due to the complex impediments of the power supply and the rest of the electrodeposit equipment operating at 20 KHz, it should be understood that the voltage measured on the substrate will not be a perfect square wave. Therefore, the applied voltage is more appropriately described using the broader term "AC pulses" instead of the less broad term of a "square wave". This conventional rule may be maintained through this description and appended claims. The resulting deposited precursor layer has a composition of Cu1.0olno.34Gao.o2Seo.9i. FIGURE 3 is a scanning electron microscope photograph of the film as it was deposited. The photograph shows that the film is airtight, densely packed and uniform. After the electrodeposition, additional In, Cu, Ga and / or Se were added to the film by physical evaporation to adjust the final composition to Culn1-xGaxSe2, the ratio of Ga / (ln + Ga) being 0.16. The films were allowed to crystallize at 550 ° C for five minutes. The temperature of the substrate (precursor film) during the physical evaporation step was also 550 ° C. The film was then selenized by exposure to selenium vapor during the low cooling time, with a cooling of about 20 ° C per minute. FIGURE 7 is an X-ray analysis that results in the electrodeposited film and the finished films of Examples 1-3. The X-ray analysis of the deposited precursor film indicates the presence of the CIGS phase and the Cu2Se phase. The adjustment of the X-ray analyzes of the film after the final film composition shows only the CIGS phase. The changes in 2-teta values are due to the different concentrations of Ga in the absorbent layers. The photovoltaic devices are completed by means of the chemical bath tank of approximately 500 A of CdS followed by the sputtering of radio frequency of 500 A intrinsic of ZnO and 3500 A of ZnO contaminated with Al203. The upper two-layer Ni / Al contacts are deposited using an e-beam system. A 100 nm anti-reflection coating of MgF2 was applied as the final step. The device was evaluated at AM1.5 illumination (1000 W / m2, 25 ° C, global ASTM E892). The device was also characterized by Auger electron spectroscopy (EEA). FIGURE 4 is the analysis of EEA that results in the finished photovoltaic cell showing the atomic distribution of the film at varying depths within the film. FIGURE 8 shows the efficiency of relative quantity of the cell as a function of wavelength. FIGURE 9 shows the Current versus Voltage Characteristics of the finished cell. The cell exhibits an overall efficiency of 12.4%. Other performance parameters for this cell are listed in Table 1 below.

Example 2 A cell was prepared according to Example 1, but the PVD step was conducted to adjust the final Ga / (ln + Ga) ratio to 0.26, instead of 0.16. The efficiency of the device improves from 12.4% to 13.2%. The analysis of EEA is shown in FIGURE 5. The relative quantity efficiency is shown in FIGURE 8. The Current versus Voltage performance is shown in FIGURE 9. Example 3 A cell was prepared according to Example 1, but the PVD step was conducted to adjust the final Ga (ln + Ga) ratio to 0.39. Overall device efficiency improved to 13.6%. The analysis of EEA is shown in FIGURE 6. The relative quantity efficiency is shown in FIGURE 8. The Current versus Voltage Performance is shown in FIGURE 9. The performance parameters for the cells of Examples 1-3 are give in Table 1 below.

Table 1 Performance Parameters for Photovoltaic Cells of Examples 1-3 Example 4 A bath containing approximately 0.016 M Cu (N03) 2 H203, 0.08 M lnCl 3, 0.08 M H2Se03 and 0.024 M Ga (No 3) 3 ( ratios of approximately 1, 5, 5 and 1.5, respectively) were prepared at a pH of 1.6. The electrodeposition proceeded to at least 2.0 volts CD and at least 2.0 volts AC at a frequency of at least 10 KHz superimposed on them. More particularly, the electrodeposit came to 3.0 VDC with an AC voltage pulse of 3.5 volts at a frequency of 20 KHz superimposed on it. The ICP composition analyzes revealed the following film compositions before and after the precursor film was finished: As deposited: Cu1.oolno.36Gao.03Se1.oo After adjustment of PVD Cu1.ooln1.04Gao.1sSe2.22 Note that the film as deposited has the highest gallium content of any of the examples presented herein. A photovoltaic device was completed as before, with the ratio of Ga / (ln + Ga) final adjusted to approximately 0.3. The final efficiency of the device was 12.3%. Example 5 An electrodeposition bath was prepared by dissolving 1.9956 gm of Cu (N03) 2-H20, 9.9531 gm of lnCI3, 1.7411 gm of H2Se03 and 12.0832 gm of Ga (No3) 3, and 15 gm of LiCl in 450 ml of water ( 0.18 M of copper ions, 0.10 of Indian ions, 0.105 M of gallium ions and 0.29 M of selenium ions). The electrodeposition proceeded to a voltage of 3.00 VDC and 3.53 VCA superimposed on them. The composition of the deposited precursor layer, expressed as 1016 atoms / cm2 was Cu .0no.46Gao.o Se ?. 6. The precursor layer was completed by PVD. The finished device exhibited a conversion efficiency of 12.3%. Example 6 A metallic precursor film of ln? -2Se? -3 was electrodeposited on coatings of glass substrates with a layer of Mo or Mo / Cu with a thickness of approximately 500 A. The precursor film was deposited using an electroplating solution. containing 2.25 gm of lnCI3 and 0.41 gm of H2Se03 dissolved in 200 ml of water. The pH of the solution was adjusted between 1.4 and 2.4 using dilute HCl (10% by volume). The films were deposited by applying a direct current voltage of 2-5 V in combination with an alternating current voltage of 0.45 V at 18.1 KHz frequency. The films had a thickness of 1-3 μm and adhered to the substrate. Example 7 A metallic precursor film of Cu1-2Se? -3 was electrodeposited on a substrate using an electroplating solution containing 6.21 gm of Cu (N03) 2-6H20 and 1.16 gm of H2Se03 dissolved in 300 ml of water. The pH was adjusted between 1.4 and 2.4 using dilute HCl (10% by volume). The films were deposited by applying a direct current voltage of 2-5 V in combination with an alternating current voltage of 0.45 V at 18.1 KHz frequency. The deposited layers were 1-3 μm thick and adhered to the substrate. Example 8 A metallic precursor film of Cu? -2ln? -2Se1-3 was electrodeposited on a substrate using an electroplating solution containing 4.47 gm of CuCI2., 5.67 gm of lnCI3 and 3.39 gm of H2SeS03 dissolved in 1050 ml of water. The pH was adjusted between 1.4 and 2.4 using dilute HCl (10% by volume). The films were deposited by applying a direct current voltage of 2-5 V in combination with an alternating current voltage of 0.45 V at 18.1 KHz frequency. The deposited layers were 1-3 μm thick and adhered to the substrate. The electrodeposited film had a poor indium content. The Indian was then added by vapor deposition by adjusting the final content to approximately CulnSe2. CdS and ZnO were added to complete the solar cell. The resulting solar cell exposed to ASTM E892-87 Global (1000 Wm "2) normal irradiation spectrum at 25 ° C. The performance parameters for the finished solar cell, having an area of 0.4285 cm2, were measured as: VQC = 0.4138 V VPmax = 0.3121V Iso = 15.40 mA lPmax = 12.96 mA Jsc = 35.94 mA cm-2 Pmax = 4.045 mW Filling Factor = 63.47% Efficiency = 9.44% The device contained only Cu-ln-Se, without any gallium. The device exhibited an efficiency of 8.76% without antireflective coating and 9.44% after an antireflective coating was added. Example 9 A precursor film of Cu? -2ln? -2Gao.o? -? Se1-3 was electrodeposited using a solution containing 1.12 gm of Cu (No3) 2-6H20, 12.0 gm of lnCl3, 4.60 gm of Ga (N03 ) 3-xH20 and 1.80 gm H2Se03 dissolved in 450 ml of water. This is equivalent to approximately 2.49 gm / l of Cu (N03) 2-6H20, 26.7 gm / l of lnCI3, 10.2 gm / l of Ga (N03) 3-xH20 and 4.0 gm / l H2Se03 and approximately 0.0084, 0.12, 0.28 and 0.31 molar copper, indium, gallium and selenium ions, respectively. The pH was adjusted between 1.4 and 2.4 using dilute HCl (10% by volume). The films were deposited by applying a direct current voltage of 2.5 V in combination with an alternating current voltage of 0.45 V at 18.1 KHz frequency. The deposited layers were 1-3 μm thick and adhered to the substrate. Example 10 A precursor film of C? -2ln1-2Ga00? -? Se? -3 was electrodeposited using a solution containing 1496 gm of Cu (No3) -5H20, 14.929 gm of lnCI3, 1.523 gm of H2Se03 and 7.192 gm of Ga (N03) 3 dissolved in 450 ml of DMSO. The films were deposited at 25 ° C and also at 50 ° C at an applied voltage of 5 VDC. EXAMPLE 11 A precursor film of Cu -2ln -2Ga0 or?.? Se1-3 was electrodeposited using a solution containing 1496 gm of Cu (N03) -5H20, 14.929 gm of lnCl3, 1523 gm of H2Se03 and 7192 gm of Ga ( N03) 3 dissolved in a mixture of 400 ml of DMSO and 50 ml of water. The films were deposited at 25 ° C and also at 50 ° C at an applied voltage of 50 VDC. Example 12 A precursor film of Cu? -2ln -2Ga00? -? Se? -3 was electrodeposited using a solution containing 1496 gm of Cu (N03) -5H20, 14,929 gm of lnCI3, 1523 gm of H2Se03 and 7192 gm of Ga (N03) 3 and 10 gm of Na2SO4 and 20 gm of LiCl dissolved in a mixture of 400 ml of DMSO and 50 ml of water. The films were deposited at 25 ° C and also at 50 ° C at an applied voltage of 50 VDC. The present invention, as described, can be incorporated into a variety of applications, such as, for example, the conversion of solar energy to electric power for power generation from the base line. Other applications include applications such as solar energy calculators, battery charges such as those used with emergency call boxes on highways, photoelectric eyes, nighttime safety light triggers, light meters for photography and other purposes, and Similar. Although the present invention has thus been described in detail with respect to the preferred embodiments and drawings and examples thereof, it will be apparent to those skilled in the art that various adaptations and modifications of the present invention can be achieved without departing from the spirit and scope. of the invention. Accordingly, it should be understood that the detailed description and the accompanying drawings as set forth above, are not intended to limit the scope of the present invention, which will be inferred only from the following claims and their legally constructed equivalents.

Claims (16)

1. CLAIMS 1. A process for preparing a copper, indium and gallium diselenide film, the process comprising the steps of: providing a substrate; provide an electrodeposition bath containing copper, indium and selenium ions, the bath also containing gallium ions in a concentration of at least 0.05 molar; insert the substrate in the electrodeposition bath; forming a semiconductor layer by simultaneously electrodeposing a film comprising copper, indium, selenium and gallium from the electrodeposition bath on the substrate, the electrodeposition process at an applied electrodeposition voltage of at least 0.5 volts; and depositing additional physical vapor deposition material selected from the group consisting of copper, indium, gallium and selenium, on the semiconductor layer to achieve a final stoichiometry for the semiconductor layer and the combined additional material, of approximately Cu? (ln1-xGax ) Se2 where x is within the scale of 0 to 1, inclusive.
2. 2. The process of claim 1, wherein x is greater than about 0.34. 3. The process of claim 1, wherein the gallium ions are obtained from gallium nitrate. 4. The process of claim 3, wherein the electrodeposition bath further comprises at least 0.3 moles of lithium chloride. 5. The process of claim 1, wherein: the indium ions are obtained from indium chloride. The process of claim 1, wherein: the electrodeposition voltage comprises a DC voltage of at least 1.0 volts and an AC voltage of at least 0.5 V at a frequency of at least 1.0 KHz superimposed thereon. The process of claim 6, wherein: the AC voltage consists of a pulse voltage. The process of claim 7, wherein the AC voltage frequency is at least 10 KHz. 9. The process of claim 8, wherein the DC voltage is at least 2 volts and the AC voltage is at least 2 volts. 10. A process for preparing a precursor film containing gallium from the photovoltaic device, the process comprising the steps of: providing a substrate; provide an electrodeposition bath containing ionic copper, indium, and selenium and gallium in the approximate relative ratios of 1, 5, 1.5 and 5, respectively; insert the substrate in the electrodeposition bath; and forming a thin film layer by simultaneously depositing copper, indium, selenium and gallium from the electrodeposition bath on the substrate. The process of claim 10, further comprising the step of: depositing the additional physical vapor deposition material selected from the group consisting of copper, indium, gallium and selenium on the thin film layer to achieve a final stoichiometry for the thin film layer and the additional material, combined, of approximately Cu? (ln -xGax) Se2 where x is within the scale 0 to 1, inclusive. The process of claim 10, wherein: the electrodeposition proceeds to an electrodeposition potential comprising a CD component of at least 0.5 volts. The process of claim 12, wherein: the additional electrodeposition potential comprises a CA component of at least 1.0 volts at a frequency of at least 1 KHz. 14. A process for preparing a precursor film containing gallium from the photovoltaic device, the process comprising the steps of: providing a substrate; provide an electrodeposition bath comprising approximately 0.01-0.02 M of copper ions, 0.05-0.15 M of indium ions, 0.05-0.15 M of gallium ions, and 0.01-0.03 M of selenium ions; insert the substrate in the electrodeposition bath; forming a film containing metals by simultaneously electrodeposing at least three elements of the electrodeposition bath on the substrate; and deposit additional vapor deposit material selected from the group consisting of copper, indium, gallium and selenium on the film containing metal to achieve a final stoichiometry for the film containing metal and the additional material, combined from approximately Cu? (ln1-xGax) Se2 where x is within the scale of approximately 0.34 to 0.50. 15. The process of claim 14, wherein the electrodeposition bath further comprises at least 0.
3. 3 M lithium chloride. 16. The process of claim 12, wherein the electrodeposition potential further includes a CA component of at least 0.5 volts.